Updated LuceneDocument to take advantage of looking up feature values…

… on existing features and selecting the max when parsing multi-value sparse vectors

docs/reference/mapping/types/sparse-vector.asciidoc

@@ -40,7 +40,7 @@ Below is an example of passing in a document with overlapping feature names.
 Consider that in this example two categories exist for positive sentiment and negative sentiment.
 However, for the purposes of retrieval we also want the overall impact rather than specific sentiment.
 In the example `impact` is stored as a multi-value sparse vector and only the max values of overlapping names are stored.
-More specifically the final `GET` query here returns a `_score` of ~1.2.
+More specifically the final `GET` query here returns a `_score` of ~1.2 (which is the `max(impact.delicious[0], impact.delicious[1]` and is approximate because we have a relative error of 0.4% as explained below)
 
 [source,console]
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@@ -89,7 +89,7 @@ GET my-index-000001/_search
 NOTE: `sparse_vector` fields can not be included in indices that were *created* on {es} versions between 8.0 and 8.10
 
 NOTE: `sparse_vector` fields only support strictly positive values.
-negative values will be rejected.
+Negative values will be rejected.
 
 NOTE: `sparse_vector` fields do not support querying, sorting or aggregating.
 They may only be used within specialized queries.